Improve the reading of .pid files from var/run

 - Only read *.pid
 - Only allow it to contain a number 


mysql-test/lib/mtr_io.pl:
  Check that the value read from pidfile is a valid number consisting only of digits
mysql-test/lib/mtr_process.pl:
  Only process .pid files in var/run dir and print a warning if other files are found there.

mysql-test/lib/mtr_io.pl

@@ -37,18 +37,16 @@ sub mtr_get_pid_from_file ($) {
     open(FILE, '<', $pid_file_path)
       or mtr_error("can't open file \"$pid_file_path\": $!");
 
+    # Read pid number from file
     my $pid= <FILE>;
-
-    chomp($pid) if defined $pid;
-
     close FILE;
 
-    return $pid if defined $pid && $pid ne '';
+    return $pid if $pid=~ /^(\d+)/;
 
-    mtr_debug("Pid file '$pid_file_path' is empty. " .
-              "Sleeping $timeout second(s)...");
+    mtr_debug("Pid file '$pid_file_path' does not yet contain pid number.\n" .
+              "Sleeping $timeout second(s) more...");
 
-    sleep(1);
+    sleep($timeout);
   }
 
   mtr_error("Pid file '$pid_file_path' is corrupted. " .

mysql-test/lib/mtr_process.pl

@@ -438,6 +438,10 @@ sub mtr_kill_leftovers () {
 
     while ( my $elem= readdir(RUNDIR) )
     {
+      # Only read pid from files that end with .pid
+      if ( $elem =~ /.*[.]pid$/)
+      {
+
 	my $pidfile= "$rundir/$elem";
 
 	if ( -f $pidfile )
@@ -459,6 +463,12 @@ sub mtr_kill_leftovers () {
 	  }
 	}
       }
+      else
+      {
+	mtr_warning("Found non pid file $elem in $rundir");
+	next;
+      }
+    }
     closedir(RUNDIR);
 
     if ( @pids )